Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Guide roll mounted for movement of its axis along arcuate...
Reexamination Certificate
1999-06-24
2001-07-24
Lorence, Richard M. (Department: 3681)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Guide roll mounted for movement of its axis along arcuate...
C474S109000
Reexamination Certificate
active
06264578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tensioner used for imparting a proper tension to a timing belt of an automotive engine or a belt for driving an auxiliary machine such as an alternator or compressor.
2. Description of the Related Art
Conventionally, the automatic tensioner is used in a transmission apparatus for transmitting a drive force of an engine to a plurality of devices by a single endless belt. The tensioner imparts a suitable tension to the belt and, at the same time, damps vibration of the belt generated due to fluctuation of the engine rotational speed or load. Thus, the drive force of the engine is reliably transmitted to the devices.
The tensioner is fixed to an engine block or in the vicinity thereof and is provided with, for example, a fixing member on which a cup is formed, an arm rotatably supported by a shaft so that it can freely rotate with respect to the cup, and a pulley attached to the front end of this arm. The arm is rotated, in a direction which presses the pulley against the belt, by a torsion coil spring provided substantially concentrically with respect to the center of rotation of the arm, by which a suitable tension is imparted to the belt. Further, as a damping mechanism for damping the vibration of the belt, a frictional member is provided between the arm and the cup. Due to this frictional member, a rotational resistance, i.e. damping force, is produced at the time of rotation of the arm, thus braking the rotation of the arm, and the vibration of the belt is damped.
In order for the pulley to constantly abut the belt and effectively damp the vibration of the belt, the arm is required to rotate relatively quickly in a direction in which the belt becomes tensioned and relatively slowly in a direction in which the belt becomes loosened. However, the above friction type damping mechanism is constituted so as to impart the same damping force in both directions, so the arm cannot rotate quickly in the direction tensioning the belt. As a damping mechanism for quickly tensioning the belt, for example, an oil pressure type damping mechanism in which an oil pressure cylinder is provided in place of the frictional member and a viscous resistance of oil is produced in only the direction in which the belt loosens is known.
However, the oil pressure type damping mechanism has a large number of parts and a complex structure in comparison with the friction type damping mechanism, therefore the cost becomes high. Further, the viscosity of the oil depends upon the environmental temperature, so the damping force is reduced in a high temperature region in comparison with that at room temperature, and the viscous resistance becomes high in a low temperature region and therefore the damping force is increased. Further, the direction of attachment is limited so as to prevent oil leakage, therefore the degree of freedom of design of the tensioner as a whole is lost and reduction of size becomes difficult.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a tensioner which reliably prevents occurrence of looseness of a belt for driving an auxiliary machine and effectively damps the vibration of the belt so as to be able to constantly hold the belt in the optimum tensioned state, while having a small size and simple structure.
According to the present invention, there is provided a tensioner comprising a fixing member, an arm, a biasing member, and a damping member.
The fixing member has a first boss. The arm has a second boss, coaxially arranged with respect to the first boss, and a pulley attached to an end portion of the arm. The arm is rotatable between a first rotation position and a second rotation position around the second boss. The biasing member urges the arm in a first direction from the second rotation position toward the first rotation position so as to tension a belt via the pulley. The damping member includes a coil spring having two end portions engaged with the first and second boss portions so as to connect the fixing member and the arm. The damping member generates a first damping force, which is a resistance against the rotation of the arm, and a second damping force larger than the first damping force so as to damp vibration of the belt. The first damping force acts upon the arm when the arm rotates in the first direction, and the second damping force acts upon the arm when the arm rotates in a second direction, which is the reverse of the first direction.
Further, according to the present invention, there is provided a tensioner comprising a first engaging portion and a second engaging portion, an arm, a biasing member and a damping member.
The first engaging portion and the second engaging portion are coaxially arranged with each other. The arm is provided with a pulley, which is engaged with an endless belt. The arm is rotatable between a first rotation position and a second rotation position around the first and second bosses. The biasing member urges the arm in a first direction from the second rotation position toward the first rotation position so as to tension the belt via the pulley. The damping member has a coil spring having two end portions engaged with the first and second engaging portions. The damping member generates a first damping force, which is a resistance against the rotation of the arm, and a second damping force larger than the first damping force so as to damp vibration of the belt. The first damping force acts upon the arm when the arm rotates in the first direction, and the second damping force acts upon the arm when the arm rotates in a second direction, which is the reverse of the first direction.
Still further, according to the present invention, there is provided a tensioner comprising a fixing member, an arm, a pulley, a biasing member and a spring type clutch.
The pulley is rotatably provided on the arm such that the pulley engages an endless belt. The biasing member urges the pulley into resilient contact with the belt, and a spring type clutch rotatably engages the arm to the fixing member. The spring type clutch includes a coil spring, that operates in conjunction with the biasing member to generate a first tightening force and a second tightening force larger than the first tightening force, and at least one of a first engaging member and a second engaging member engaged with the coil spring to produce a first rotational resistance that corresponds to the first tightening force and a second rotational resistance that corresponds to the second tightening force. The first rotational resistance occurs in a first rotational direction of the arm, and the second rotational resistance occurs in a second rotational direction which is opposite to the first rotational direction.
Further, according to the present invention, there is provided a tensioner comprising a pulley, an arm, a biasing member, a fixing member and a spring type clutch.
The pulley resiliently contacts an endless belt, and the arm rotatably engages the pulley on a first rotational axis. The biasing member urges the arm in a first direction so that the pulley tensions the belt. The fixing member rotatably engages the arm on a second rotational axis parallel to the first rotational axis, and a spring type clutch rotatably connects the arm and the fixing member. The spring type clutch, operating in conjunction with the biasing member, generates a first rotational resistance in the first direction and a second rotational resistance larger than the first rotational resistance in a second direction, which is opposite to the first direction.
REFERENCES:
patent: 4392840 (1983-07-01), Radocaj
patent: 4473362 (1984-09-01), Thomey et al.
patent: 4583962 (1986-04-01), Bytzek et al.
patent: 4822322 (1989-04-01), Martin
patent: 5470280 (1995-11-01), Ayukawa
patent: 5620385 (1997-04-01), Cascionale et al.
patent: 5803849 (1998-09-01), Ayukawa
patent: 3718227 (1988-12-01), None
patent: 4010928 (1991-10-01), None
patent: 19813586 (1999-09-01), None
patent: 11-13843 (1999-01-01)
Greenblum & Bernstein P.L.C.
Lorence Richard M.
Unitta Company
LandOfFree
Belt tensioner with vibration damping function does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Belt tensioner with vibration damping function, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Belt tensioner with vibration damping function will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2526219